Exposure to Wood Dust Among Carpenters in the Construction Industry in The Netherlands

Exposure to wood dust was measured among 26 carpenters at 13 building projects. Sampling days were chosen randomly. Individual tasks, based on technology applied and material used during a working day, were sampled separately. From these task-based measurements, 8 h time-weighted average concentrations were calculated. Sampling was performed in accordance with a protocol that was developed by the carpentry and furniture industry and which was especially designed for sampling of wood dust. Eight hours time-weighted average exposure to wood dust ranged from 0.8 to 11.6 mg m(-3) with a geometric mean (GM) of 3.3 mg m(-3) and a geometric standard deviation (GSD) of 2.1. The probability of exceedance of the OEL, when comparing the estimated concentrations against the Dutch OEL of 2 mg m(-3), was 75%. The highest exposures were measured during sawing of Cempanel sheets. Task-based measurements showed lowest exposures when working outdoors (n = 11, AM = 2.2 mg m(-3)), but even then 5 out of 11 task-based exposures exceeded 2 mg m(-3). Indoors the exposure was 5.2 mg m(-3) (AM, n = 29) and when working both indoors and outdoors exposure was 16.2 mg m(-3) (AM, n = 4). In conclusion, long-term average exposure to wood dust among carpenters at construction sites is more than 1.5 times the present occupational exposure limit of 2 mg m(-3). The estimated probability of exceedance of the OEL was 75% and a reduction of exposure with a factor 5 is needed to bring the probability of exceedance below 5%. It is intended to lower the exposure limit to 1 mg m(-3) by 1 January 2007. In that case the probability of exceedance of the OEL is 95% and a reduction of exposure with a factor 10 is needed to bring the probability of exceedance below 5%. This can be achieved by using alternative materials, preparation of building material in workshops equipped with exposure controls, alternative equipment and improved ventilation and good housekeeping.

Evaluation of HUD-funded lead hazard control treatments at 6 years post-intervention

The Evaluation of the HUD Lead-Based Paint Hazard Control Grant Program (Evaluation) was a HUD-funded study of the effectiveness of lead hazard control (LHC) treatments conducted by 14 grantees in communities across the country. A stratified random sampling scheme was used to select treated units at four grantee sites for continued environmental assessment at 6 years post-intervention. The study compared the relative effectiveness after 6 years of the different classes of interventions used by the grantees, after controlling for such factors as housing conditions and characteristics and resident and neighborhood characteristics. Geometric mean dust-lead levels on floors and window sills were 11% and 23% lower, respectively, at 6 years post-intervention than at any preceding point following the intervention. Although geometric mean window trough dust-lead levels were slightly higher at 6 years post-intervention than at other post-intervention time periods, they were still over 75% lower than before intervention. Treatment at more-intensive levels was associated with lower window sill and window trough dust-lead levels; however, statistical modeling found no significant difference in floor dust-lead loadings over time between the levels of treatment; however, significant differences in window sill and window trough dust-lead levels between treatment levels were evident. Findings from the 6-Year Extension study indicate that across all grantees and treatment strategies the treatments applied were effective at significantly reducing environmental lead levels on floors, window sills, and window troughs at least 6 years following the intervention.

Effects of the prolonged vertical tube on the separation performance of a cyclone

This article aims at the gas flow into the dustbin of conventional cyclones, the prolonged cyclone (attaching a vertical tube at the bottom of the dust outlet) is proposed by some researchers, which can make flow with dust enter into the tube and separate further. The Reynolds stress transport model (RSTM) has been employed to predict the gas flow fields of the conventional and prolonged cyclones. The tangential velocity, axial velocity profiles and turbulent kinetic energy profiles are presented, and the downward flow rates into the dustbin of the three cyclones are compared. The separation performances of these three cyclones are tested. The result indicates that the tangential velocity, axial velocity and turbulent kinetic energy in the dustbin reduce greatly when the prolonged vertical tube attaching into the dust outlet, which can avoid the re-entrainment of already separated dust effectively. Furthermore, the prolonged vertical tube increases the separation space of dusts. The downward flow rate into the dustbin of the prolonged cyclone decreases compared with the conventional cyclone. The experimental results show that the prolonged vertical tube can improve the separation efficiency by a slightly increased pressure drop. However, for an even longer tube, the separation efficiency is slightly reduced. Thus, there is an optimal tube length for a given cyclone.

Prediction of particulate loading in exhaust from fabric filter baghouses with one or more failed bags

Loss of filtration efficiency in a fabric filter baghouse is typically caused by bag failure, in one form or another. The degree of such failure can be as minor as a pinhole leak or as major as a fully involved baghouse fire. In some cases, local air pollution regulations or federal hazardous waste laws may require estimation of the total quantity of particulate matter released to the environment as a result of such failures. In this paper, a technique is presented for computing the dust loading in the baghouse exhaust when one or more bags have failed. The algorithm developed is shown to be an improvement over a previously published result, which requires empirical knowledge of the variation in baghouse pressure differential with bag failures. An example calculation is presented for a baghouse equipped with 200 bags. The prediction shows that a small percentage of failed bags can cause a relatively large proportion of the gas flow to bypass the active bags, which, in turn, leads to high outlet dust loading and low overall collection efficiency from the baghouse.

Fine dust filtration using a metal fiber bed

A bed-type filter composed of thin metal alloy fiber was closely examined with dust capturing in cold and hot runs. The investigation of an individual mechanism across the filter bed indicated that the aerated dust could be initially collected by depth filtration, and after a while, surface filtration dominated the overall dust collection. The present metal fiber bed was comparable to the conventional ceramic filters because of its good collection efficiency with low pressure drop. It also showed potential to be used as a prefilter in a diesel exhaust trapping system.

The implications of integrated assessment and modelling studies for the future remediation of chromite ore processing residue disposal sites

Chromite ore processing residue (COPR) waste from a former chromium chemical works (1830-1968) is still contaminating groundwater in Glasgow, Scotland, with carcinogenic hexavalent chromium, Cr(VI). An integrated analytical, experimental and modelling approach has identified and accounted for mineral phases and processes responsible for the retention and release of Cr(VI) under prevailing field conditions. Both the nature of mineral phase retention and the buffered high pH of the sites, however, militate against direct remediative treatment of the source material, for example by the application of generic methods (e.g. FeSO4) that have been successfully employed elsewhere for the reduction of Cr(VI) to Cr(III) in other matrices. The interception and treatment of groundwater to remove Cr(VI) and the capping of sites to reduce human exposure to airborne Cr(VI)-contaminated dust may well be more realistic and effective, at least in the short to medium term.

Dust collection efficiency analysis in a two-dimensional circulating granular bed filter

Dust collection efficiency data were analyzed to determine better operating conditions for a two-dimensional circulating granular bed filter (CGBF). The dust collection efficiency in the granular bed was affected by the following operating parameters: the louver angle, the solids mass flow rate, and the particle size of the bed material. Experimental results showed that higher dust collection efficiency occurs when the solids mass flow rates were 20.34 +/- 0.24, 21.50 +/- 0.11, and 30.51 +/- 0.57 g/sec at louver angles of 45 degrees, 30 degrees, and 20 degrees, respectively. Optimal dust collection efficiency peaked with a louver angle of 30 degrees. Average particle sizes of bed material by sieve diameters (microm) of 795 microm had higher dust collection efficiency than the average collector particle size of 1500 microm. Dust collection efficiency is influenced by bed material attrition phenomenon, causing dust collection efficiency to decrease rapidly. The dust collection efficiency analysis not only found the system free of design defects but also assisted in the operation of the two-dimensional CGBF system.

What's driving Twin Cities air quality?

Air quality affects the health of patients, particularly those with asthma, COPD, cardiovascular disease, and other heart problems. Epidemiological studies show that common air pollution may have health effects in sensitive populations even when the air quality is within Environmental Protection Agency standards. In Minnesota, the main 2 pollutants of concern are ozone and fine particles. Emissions from motor vehicles are a major source of each. This article discusses these pollutants and reports on the work of the Minnesota Pollution Control Agency in measuring air quality and alerting the public about air-quality problems.

Silica exposure on construction sites: results of an exposure monitoring data compilation project

To expand on the limited size and scope of construction silica exposure studies, a silica monitoring data compilation project was initiated through the American Conference of Governmental Industrial Hygienists Construction Committee. Personal silica exposure monitoring data was collected and analyzed from 13 private, research, and regulatory groups. An effort was made to collect as much detail as possible about task, tool, and environmental and control conditions so as much information as possible could be garnered. There were considerable data gaps, particularly with regulatory agency data, that represented over half of the data set. There were 1374 personal quartz samples reported with a geometric mean of 0.13 mg/m(3) and a GSD of 5.9. Descriptive statistics are reported by trade, task, tool, and data source type. Highest exposures were for abrasive blasters, surface and tuckpoint grinders, jackhammers, and rock drills. The sample period was important, with short-term samples (up to 2 hours) having considerably higher levels than midterm (2-6 hours) or longer (over 6 hours) samples. For nearly all exposure variables, a large portion of variable categories were at or over the quartz occupational exposure limit of 0.05 mg/m(3), including 8 of 8 trade, 13 of 16 task, and 12 of 16 tool categories. The respiratory protection commonly used on construction sites is often inadequate for the exposures encountered. The data variability within task and tool was very large, with some very high exposures reported for a broad spectrum of tools. Further understanding of the conditions leading to high exposures will require more detailed documentation of the sample characteristics following database design recommendations or systematic surveys of exposure in this complex industry.

Lead dust in Broken Hill homes: effect of remediation on indoor lead levels

This study was undertaken to determine whether home remediation effectively reduced indoor lead levels in Broken Hill, a long-established silver-lead-zinc mining town in outback Australia. A before-after study of the effect of home remediation on indoor lead levels was embedded into a randomized controlled trial of the effectiveness of remediation for reducing elevated blood lead levels in young children. Moist towelettes were used to measure lead loading (microg/m2) on internal windowsills and internal and entry floors of 98 homes; samples were collected before, immediately after, and 2, 4, 6, 8, and 10 months after remediation. Data were log(10) transformed for the analysis. Remediation reduced average indoor lead levels by approximately 50%, and lead levels remained low for the duration of the follow-up period (10 months). The greatest gains were made in homes with the highest initial lead levels; homes with low preremediation lead levels showed little or no benefit. Before remediation, homes located in areas with high soil lead levels or with "poor" dust proofing had higher lead levels than those in areas with lower soil lead levels or with "medium" or "good" dust proofing; these relative differences remained after remediation. There was no evidence that lead loading was reduced by an increased opportunity to become aware of lead issues. We conclude that remediation is an effective strategy for reducing the lead exposure of children living in homes with high indoor lead levels.

Effect of spraying biological additives for reduction of dust and bioaerosol in a confinement swine house

The aim of this on-site experiment is to evaluate and compare efficiencies of currently utilized biological additives to reduce emissions of dust and bioaerosol in a confinement swine house. The mean reduction rate of total dust only after spray ranged was approximately 30% for all the treatments, compared to initial level before spraying additives which was found to reduce the initial level of total dust significantly (p < 0.05). The mean reduction rate of all the treatments at 1 hr after spraying was about 24% which was 6% lower than only after spray. Since 3 hr after spraying, however, total dust level fluctuated inconstantly for all the treatments, besides application of soybean oil. The mean reduction rates of all the treatments only after spraying as compared to initial level before spraying were about 53% for total airborne bacteria (p < 0.01) and 51% for total airborne fungi (p < 0.01), respectively. At 1 hr after spraying, the reduction rate of total airborne fungi averaged to about 35% for all the treatments (p < 0.05), while insignificant reductions of total airborne bacteria were found only in the treatments with salt water, soybean oil, artificial spice, and essential oil (p > 0.05). The fluctuations of total airborne bacteria and fungi, which were similar to total dust, were observed for all the treatments 3 hr after spray.

Encasement of bedding does not improve asthma in atopic adult asthmatics

AIM

We evaluated the impact of impermeable bed covers on asthma in asthmatics with clinically relevant house dust mite (HDM) sensitization.

METHODS

The study included 32 HDM-sensitized asthmatics in whom HDM allergy was considered as a significant factor in their asthma. They were randomized into either an intervention group whose bedding was encased with impermeable covers, or a control group who received cotton covers. Before and 3 and 6 months after encasement, dust samples were collected from the bedding and assayed for Der p 1. Clinical outcomes included quality of life, lung function, bronchial reactivity to methacholine, symptoms, medications and peak flow rates.

RESULTS

Baseline Der p 1 levels in both the active and the placebo groups were comparable and high (19.2 vs 18.9 microg/g of dust). There was a significant reduction in Der p 1 levels in the active group after 6 months, but not in the placebo group (7.3 vs 21.9 microg/g of dust). Quality of life improved significantly in both the intervention and control groups, but there was no significant difference in the improvements between the groups. There was no significant change in lung function, symptoms, and requirements for medications.

CONCLUSIONS

Encasement of bedding significantly reduced the Der p 1 levels. However, this was not sufficient to produce worthwhile clinical improvement in those in whom dust mite avoidance might well have been recommended as part of their clinical management.

Fine particulate matter national ambient air quality standards: public health impact on populations in the northeastern United States

In this article we identify the magnitude of general and susceptible populations within the northeastern United States that would benefit from compliance with alternative U.S. Environmental Protection Agency (EPA) annual and 24-hr mass-based standards for particulate matter (PM) with an aerodynamic diameter < or = 2.5 microm (PM2.5). Understanding the scale of susceptibility in relation to the stringency or protectiveness of PM standards is important to achieving the public health protection required by the Clean Air Act of 1970. Evaluative tools are therefore necessary to place into regulatory context available health and monitoring data appropriate to the current review of the PM National Ambient Air Quality Standards (NAAQS). Within the New England, New Jersey, and New York study area, 38% of the total population are < 18 or > or =65 years of age, 4-18% of adults have cardiopulmonary or diabetes health conditions, 12-15% of children have respiratory allergies or lifetime asthma, and 72% of all persons (across child, adult, and elderly age groups) live in densely populated urban areas with elevated PM2.5 concentrations likely creating heightened exposure scenarios. The analysis combined a number of data sets to show that compliance with a range of alternative annual and 24-hr PM2.5 standard groupings would affect a large fraction of the total population in the Northeast. This work finds that current PM2.5 standards in the eight-state study area affect only 16% of the general population, who live in counties that do not meet the existing annual/24-hr standard of 15/65 microg/m3. More protective PM2.5 standards recommended or enacted by California and Canada would protect 84-100% of the Northeast population. Standards falling within current ranges recommended by the U.S. EPA would protect 29-100% of the Northeast population. These considerations suggest that the size of general and susceptible populations affected by the stringency of alternative PM standards has broad implications for risk management and direct bearing on the U.S. EPA's current NAAQS review and implementation.

Effectiveness of lead-hazard control interventions on dust lead loadings: findings from the evaluation of the HUD Lead-Based Paint Hazard Control Grant Program

From 1994 to 1999, the Evaluation of the US Department of Housing and Urban Development Lead-Based Paint Hazard Control Grant Program studied the intervention experiences of over 2800 homes in 11 states in the USA. Each interior intervention was categorized as (in order of increasing intensity) (a) cleaning/spot painting; (b) complete repainting; (c) complete repainting plus window treatments; (d) window abatement plus treatments to other components; (e) abatement of all lead-based paint hazards; or (f) abatement of all lead-based paint. Complete dust testing and environmental data were available for 1034 and 278 dwellings through 12 and 36 months postintervention, respectively. Strategies ranging from complete repainting to window abatement plus other treatments reduced geometric mean preintervention windowsill and floor dust lead loadings up to 36 months postintervention (reductions for complete repainting, from 16 to 5 microg/ft2 on floors and 182 to 88 microg/ft2 on sills; for window abatement plus other treatments, 27-8 microg/ft2 on floors and 570-124 microg/ft2 on sills). Full abatement reduced windowsill and floor loadings from baseline to 12 months postintervention [95-6 microg/ft2 on floors and 518-30 microg/ft2 on sills (data were not available for this strategy at 36 months)]. Window lead-hazard abatement was the most effective measure to reduce dust lead loadings on windows, but this treatment would need to be performed in conjunction with treatments to floors as well as exterior and soil treatments for the most effective control of dust lead on floors.

Change in the World of Occupational Health: Silica Control, Then and Now

To control silicosis, we need to understand how change happens in occupational health. Science alone does not drive policy, because we have known the causes of silicosis, and how to prevent it for decades, yet the disease persists. To control occupational disease, we need to enter the social realm of work. To investigate the determinants of a successful silicosis control program, we wrote a social history of the Vermont Granite Industry from 1938 to 1960, examining union journals, newspapers, industry journals, scientific literature and government documents, and interviewing key informants. The crucial factor of the successful program was a strong public health movement to control tuberculosis, rather than pressure to control the occupational disease. Using this lesson, to protect workers from silica exposure now, we chose to regulate silica under an environmental law, the Massachusetts Toxics Use Reduction Act. Science is but one small factor, necessary but insufficient, in policy change. We in occupational health need to hitch onto a stronger movement, currently the environmental movement. Where unions are too weak to demand safe technologies, we need to learn to speak the language of employers, because they may have little idea of the costs of interventions. We need to gather more economic information about the costs of interventions.

Evaluation of Misting Controls to Reduce Respirable Silica Exposure for Brick Cutting

It is estimated that more than 1.7 million workers in the United States are potentially exposed to respirable crystalline silica, with a large percentage having been exposed to silica concentrations higher than the limits set by current standards and regulations. The purpose of this study is to characterize the use of water-misting engineering controls to reduce exposure to respirable crystalline silica for construction workers engaged in the task of brick cutting. Since data concerning the efficacy of engineering controls collected at worksites is often confounded by factors such as wind, worker skill level, the experiments were conducted in a laboratory environment. A completely enclosed testing chamber housed the brick-cutting saw. Respirable dust concentrations were measured using the Model 3321 Aerodynamic Particle Sizer. Specifically, the laboratory experiment was designed to compare dust suppression through water misting using conventional freely flowing water techniques. Brass atomizing nozzles with three flow rates were used for making this comparison: low (5.0 ml s(-1) or 4.8 gal h(-1)), medium (9.0 ml s(-1) or 8.6 gal h(-1)) and high (18 ml s(-1) or 17.3 gal h(-1)). The flow rate for freely flowing water, using manufacturer-supplied equipment, was 50 ml s(-1) (48 gal h(-1)). The experiment consisted of five replications of five samples each (low-misting, medium-misting, high-misting, freely flowing water and no control). The order of sampling within each replicate was randomized. Estimates of dust reduction showed that low-misting nozzles reduced the respirable mass fraction of dust by about 63%, medium-misting nozzles by about 67%, high-misting nozzles by about 79% and freely flowing water by about 93%. Based on these results, it may be feasible to use misting to control respirable silica dust instead of freely flowing water. This strategy is of practical interest to the construction industry which must frequently limit the amount of water used on construction sites.

Effects of using retention-pond water for dust abatement on performance of feedlot steers and carriage of Escherichia coli O157 and Salmonella spp

OBJECTIVE

To evaluate the effects of using retention-pond water for dust abatement on performance of feedlot steers and carriage of Escherichia coli O157 and Salmonella spp.

DESIGN

Matched cohort studies.

ANIMALS

2 groups of feedlot steers comprising 3,510 (pathogen carriage) and 3,737 (performance) animals housed in a large commercial feedlot in the Texas Panhandle.

PROCEDURE

Steers were systematically allocated to treatment pens approximately 60 days after arrival (pathogen carriage) or at arrival (performance). For evaluation of pathogen carriage, feces and hide swab specimens were collected from 25 animals in each pen within 10 days of slaughter. Samples were submitted for bacterial culture for E. coli O157 and were tested with a polymerase chain reaction-based assay for Salmonella spp. For evaluation of performance, pen weights of animals were obtained at arrival and slaughter and feed delivered to each pen was recorded. The exposure of interest for both studies was application of retention-pond water through fixed high-pressure sprinklers.

RESULTS

Carriage of E. coli O157 and Salmonella spp and animal performance were not adversely affected by exposure to retention-pond water. Prevalences of E. coli O157 in feces, on hides, and either in feces or on hides for those exposed to retention-pond water were 8.3%, 8.9%, and 15.4%, respectively; prevalences for those unexposed to retention-pond water were 11.4%, 15.4%, and 22.6%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that use of retention-pond water for dust abatement in feedlot pens does not adversely affect pathogen carriage or animal performance.

[Ergonomic improvements obtained by the realization of an automatic methane cylinder-storage system in a control station]

In a control station where liquid-methane cylinder for vehicle transport are inspected, the realization of an automatic cylinder-storage system not only managed to reduce space shortage inside the plant so avoiding possible accidents due to collisions between fork lift trucks and gathered cylinders or lorries, but also noticeably improved environment by reducing noise, total dust concentration and whole body vibration transmitted through the seats to lift truck operators.